Solar Events

The Evolution Of Life on Our Planet

« continued from photosynthesis and the sun
While this process is the means by which our food is generated, and so is very much a phenomenon of nature today, it is hard to draw a line between today and the deep past because it is this very phenomenon that is responsible—in part—for our existence as human beings at all. Our warm blood, our breathing, the multicellular fabric of our body and mind (a trillion cells working together)—all have been brought forth from nature by the direct and indirect effects of photosynthesis. But it goes much further than that. The land on which our food grows and the water that comes down as rain that has evaporated out of the oceans—these too have been, in part, created or sustained by this process. So intimate is the mutuality between life and the planet’s physical features that we are looking at a single, very densely integrated system. Life and Earth have an entwined history, so much so, that it is not possible to separate out one from the other in any meaningful way. This history has been fueled by the continuous arrival of photons of light from the Sun. Thus, learning about and reflecting on the power of photosynthesis, we find ourselves drawn inexorably out to the cosmos in which our lives are lived. There is more to that mouthful of bread than meets the eye!

Photosynthesis has enabled life to occur and to become complex. Its chemical effects have altered both the rocks and the atmosphere. Today, industrialized society digs up the transformed remains of ancient life and we drive around in our cars, turn on our computers and much more, as a result of this infusion of life’s products into the body of Earth over millennia. But the most striking effect has been on the delicate molecular-based process of evolution by the release of a fiery, dynamic element into the atmosphere—oxygen. The endlessly shifting molecules of DNA, with their control over all other molecules of the body, have been especially sensitive to environmental changes in the quantity of oxygen. With that sensitivity has come much change.

Life extended its powers with the aid of oxygen and gained a vitality and strength through which it has covered all parts of the planet. At each stage of the evolution of life, oxygen levels (and the formation of an ozone layer from that oxygen) have played an absolutely critical role. From eukaryotes to the first animals and plants, to land-living beings breathing in the atmosphere through lungs, to the warm-blooded, even more energetic and more emotionally expressive mammals, oxygen is deeply implicated as a potent factor of change and empowerment. Thus, the spiraling process of evolution is all wrapped up with this primordial relationship of photosynthesizing organisms and the Sun. But how does the magic of photosynthesis actually work? How does it produce life?

The Process of Photosynthesis

Photosynthesis is an incredibly complex process. How the single-celled organism or the chloroplast manages to split water, for instance, is still not fully understood. In essence, however, what it involves is the controlled and coordinated use of incoming energy from the Sun to “fire” the capacity of the organism to synthesize—in a sequence—two main kinds of molecules. The first of these molecules supplies the power to forge the second. It is the ubiquitous energy-carrying molecule that we, like all animals, can also make but only as a result of eating— Adenosine Triphosphate or ATP. With the freshly-minted power of ATP the organism can then make its carbohydrates, which are longer-lasting energy molecules needed for life’s processes. It pulls in carbon dioxide from the environment, dismantles it, and then weaves its carbon together with hydrogen and oxygen in a very complex circular process involving an enzyme to speed reactions along. The totality of chemical reactions produce more oxygen than is needed and the surplus floats out into the environment. Photosynthesis thus fulfils its ultimate goal of integrating precious carbon into the organism, for life can only happen with this particular element being available. Its propensity to form bonds with other elements, as well as itself, makes it essential for the self-organization of the body to occur at all. It is the glue from which a body can be made. Thus, photosynthesis is the first stage in the wider process of enabling life.

1 Comment so far

  1. Rick Johnson June 25th, 2007 8:02 pm

    If we are ever going to satisfy our thirst for energy, we must integrate into the existing natural system. Photosynthesis is definitely the key. Using photosynthesis that requires water to produce hydrogen and oxygen in nature’s way of producing energy, otherwise known as life. Burning hydrogen produces water, and the cycle comes full circle. Such a completely self-sustaining cycle is our only hope.

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